Furnace.



No. 726,114. PATENTED APR; 21, 1903.

R. THOMSON.. PURNAGE.:

APPLICATION FILED AUG. 21. 1902.

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No. 726,114. PATENTED APR, 21, 1903. R. THOMSON.

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APPLIGATION FILED AUG". 21. 1902,

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UNITED STATES@ :PATENT OFFICE.

ROBERT THOMSON, OF GLASGOW, SCOTLAND.

FU RNACE.

SPECIFICATION forming part of Letters Patent N o. 726,114, dated April 21, 1903.

l -V ldpplicatipn filedhAugust l21, 1902. Serial No. 120,599. (No model.)

and in Germany, dated February 1.4, 1902,) of

which the following'is aspecification.l

My invention relates to: impro'vvem'ents,in the apparatus for the combustion'of solid, r pulverized, liquid, and gaseous fuel, and my improvements are applicable to kilns, refusedestructors, furnaces for the melting of metals or smelting ores, and to boiler and all other types of furnaces. j

direct to the gases evolved therefrom,. the principal supply of Aairalwaysl enteringlthe fuel by one surface, passing through it, and, together with the generated gases, emerging from and leaving by another surface. The

air is often supplied4 under v,iorced or inf-y duced draft and'i'sals'o sometimes previously heated.

When combustion has been started, the; green fuel if it be capable of distillation'flrstvv distils under the action of the heat generated supplying'ofair largely in excess of that which 4can be utilized in combustion, the gases being thus burned more or less completely on their Way to the chimney and quite apart from and without the assistance of the incandescent fixed portion of the fuel.

By this method of Working complete combustion is seldom or never attained and some of the gases pass away unburned, either owing to a deficiency of the air-supply or if the air-supply be sufficient owing to the cooling effect of the air on the gases before the necessary intimate admixture of air and gases can be effected, thus preventing the attainment of the high temperature necessary for the maintenance of combustion.

My invention therefore has for its object to secure concentrated and complete combus- `tion of the fuel Vpracticallywithout the usual ,excessjof oxygen in such a manner that the maximum .temperature available from the fuel and the best heating'eect may be produced,` maintained', and utilized.

, My improved furnace consists in a closed chamber,on the bottom of which the fuel rests ,n 1 when solid fuel is used loron the bottom of In furnaces for the comb'ustionof solid fuelas hitherto generally employed the air is Asup-j plied either to pass wholly'through the fuelg 'or to pass partly through the fuel and partly which the air and fuel plays when pulverized, liquid, vor gaseous fuel is employed, and

`which is provide`d, ac'cor ding to the size of hearth, with one or moretubular roof-open- -ingsof length'grve'at in proportion to their diamete'rau opening being also formed in the chamber abovevthe fuelsurface for commu- According to my invention `in the combustion of liquid, pulverized, and gaseous fuel the fuel is preferably introduced with the air against a surface consisting of a bed of coarsely-broken refractory material, or the broken refractory material may be replaced by carbon, which combines with any excess of oxygen, and thus automatically adjusts any disparity in the proportion of ai-r and fuel when air is in excess of the fuel-supply. Complete combustion of'thisfu'el'may thus be obtained practical-ly without excess of Oxyseu- In the accompanying drawings, Whih'illustrate one form of furnace embodying my invention, Figure l is an elevation of the furnace in part section. Fig. 2 is a complete sectional elevation of the furnace, the section being taken on a plane at right angles to that of Fig. l. Figs. 3 to 5 illustrate, by Way of example, one mode of applying myimproved ICO furnace for steam raising in a Lancashire boiler. Fig. 3 is a front elevation of the furnace and boiler. Fig. 4 is a plan of Fig. 3, and Fig. 5 is a sectional elevation on the line A Bof Fig. 4. In this figure the trolley structure which supports the furnace is not shown in section.

Corresponding parts are designated by the same reference-letters in the several figures.

The furnace consists of a chamber a, which may be of rectangular or other suitable section in plan, and is provided with a heat-resisting inclosing wall b, of fire-brick or other suitable material, lining an external metal casing c. Between the casing and the firebrick lining h is interposed a packing d, of material which is a nou-conductor of heat.

The furnace is provided with a door e to enable the ashes and clinker to be readily removed.

In the side wall of the chamber I provide an opening f, through which the highly-heated products of combustion escape under natural chimney-draft or through which they may be withdrawn by means of a mechanical draft-inducing appliance, such as a fan, or by means of a steam-blast introduced into the chimney-flue.

To supply the air for combustion, I provide one or more tubular roof-openings, such as g, which is preferably trumpeted out toward its upper end, so as to secure the maximum flow of air through the tube. The tube g is of relatively small sectional area to that of the exhaust-opening f, so that the air acquires a high velocity in passing through the tube into the furnace. The tube is also of considerable length in relation to its diameter in order to give direction to the entering air-stream.

In the working of the furnace the reduction of pressure which is produced within the chamber a, by the chimney or otherdraft employed causes a powerful stream of air to pass in through theY tube g with great velocity and strike downward through the highly-rareed gases in the furnace with considerable force onto the fuel or other material capable of becoming incandescent placed on the hearth. The quantity of air supplied, the force of its impact, and the consequent consumption of fuel are dependent on the strength of the eX- haust through the opening f. The direction of the entering air-stream being substantially opposed to that of the highly-rareiied combustion-gases, the air is brought into immediate and intimate contact with the incank descent fuel and emerging combustible gases at the point of their emission from the fuel. These gases are driven back by means of the steady stream of air playing on the fuel and are burned in contact or in conjunction with the incandescent solid portion of the fuel or other material on the hearth. The fuel is thus completely burned practically within the chamber itself, producing more intense combustion than would be the case if the solid and gaseous parts of the fuel were burned apart from each other. The fuel is fed through the tube g, and the feed may be conducted by hand in the usual way, or any wellknown form of mechanical appliance may be provided for enabling an automatic continuous feed through the tube to be effected in regular working of the furnace. Where liquid, pulverized, or gaseous fuel is to be burned, the fuel is charged into the tube g, so that it is carried into the furnace with the air-stream, and thus this pulverized, gaseous, or liquid fuel is subjected to the velocity of the enteringair-currentandisimpelled therebyagainst the bed of incandescent material, and the said fuel or the gases evolved therefrom are driven deeply into the incandescent bed. In the combustion of liquid and gaseous fuel the hearth or bottom of the furnace is preferably covered with a bed of pieces of broken refractory material onto and among which the mixed stream of fuel and air plays, complete combustion being effected in a similar manner to that of solid fuel. Instead of pieces of broken refractory materialI may place pieces of carbon, such as coke, on the hearth, so as t0 insure the production of a flame which is neutral-that is,containing neither unburned gases nor oxygen.

In order to obtain the best results in working the furnace, the feeding of the fuel should be as nearly as possible continuous and the fuel-surface or the surface of refractory material should be maintained within such a distance from the lower extremity of the tube g that the air discharging from the tube preserves its columnar or stream-like fo'rm until it strikes the fuel, and in order that the products of combustion may be withdrawn from the chamber without interfering with the inflowing air-stream I cause the air-supply tube g to depend from the roof of the furnace so that its lower extremity is beneath the level of the exhaust-outlet f.

The height of the roof above the fuel-surface should be such as to secure the maximum reverberatory heating effect consistent with the provision of sufficient space for the eX- pansion of the gases by combustion, for by means of the heat reflected from the roof the charges of fresh fuel introduced into the furnace attain the combustion temperature with great rapidity. W'hen solid fuel is used, it becomes almost instantlyignited on the upper surface by the reverberated heat, so that by the action of the air-blast combustion is more rapidly propagated downward.

I have found furnaces to work well when constructed with air-inlet tubes fifteen inches long and two and three-quarter inches internal diameter, one tube being provided over each square foot of hearth-surface and with the area of the outlet for the combustion products about seven times the area of the airinlet ports. The distance between the hearth on which the fuel rests and the lower end of the air-inlet tube was about twelve inches IIO IIS

and the fuel mass was maintained at a level about four inches below the end of the tube. Such a furnace with an air suction equal to eight-tenths of an inch of water at the outlet from the furnace burns without smoke about fifty pounds weight of washed bituminous nut coal per square foot per hour.

When the furnace is worked with an airsupply at ordinary temperaturematu ral chimney-draft is usually sufficient to maintain a powerful blastof air through the tube g; but by employing a mechanical draft appliance for diminishing the pressure within the furnacea further increase in the power of the blast can be obtained. Heated air may be supplied to the furnace by providing a side communication between the tube g and a supply of hot air, the upper end of the tube be` ing closed to atmosphere and only used for feeding the fuel into the furnace; but in this case the effect of the draft requires to be increased in order to compensate for the diminished density of the air by increasing its speed, so that it may be supplied in quantity sufficient for combustion of the fuel.

The method Vof combustion which I have described above may be employed with advantage for many purposes-for example, steam-raising, steelsmelting, ore-smelting, and the distillation of gas from fuel in kilns and other furnaces. Figs. 3 to 5 illustrate one of its applications in which my improved furnace is shown adapted to a Lancashire boiler. The furnace is of the same construction as that described above; but instead of a single air-inlet tube g I provide a number of such tubes, so as to supply the volume of air necessary for combustion of the larger fuel-body employed'. The furnace is provided with two exhaust-outlets f, to which are attached short lire-resisting tubes or flues h, adapted to iit into the boiler-nues t', as shown in Figs. 4 and 5. In order that access to the boiler-flues may be readily obtained for cleaning or other purposes, the furnace is attached to atrolleyframe j, supported by wheels 7c on rails Z, thereby enabling the furnace to be moved bodily away from the boiler and returned into position again. The joint between the out-V side of the tubes k and the boiler-fines should be made air-tight in any convenient mannerfor example, by means of a luting of clay or lime-so as not to impair the efficiency of the flue-draft in the working of the furnace.

Having now described my invention, what Iclaim as new, and desire to secure by Letters Patent, is-

1. A furnace for burning combustible material comprising a hearth for supporting incandescent material and'closed against the entrance of air from below, said furnace having a combined air and fuel inlet opening above the hearth arranged to direct the aircurrent so as to impinge directly upon the incandescent material with its full Velocity and an outlet for the products of combustion above the bed of incandescent material and above the lower end of the inlet, said outlet being of greater capacity than the air-inlet whereby rarefaction is produced within the furnace, said furnace being closed above the bed of incandescent material against the inlet of fuel except through the said air-inlet, the fuel being subjected to the velocity of the air and being deposited on the area upon which the air-current impinges, substantially as described.

2. A furnace for burning combustible ma-` terial comprising a horizontal hearth for supporting incandescent material with its upper surface substantially horizontal and closed against the passage of air from below, said furnace having a combined fuel and air in let opening above the hearth arranged to di rect the air and fuel at right angles to the bed of incandescent material and an outletopening above the hearth of larger area than that of the inlet-opening, said furnace being closed above the bed of incandescent matei rial against the inlet of fuel excepting through the said air-inlet, the fuel being deposited on the area upon which the'air-current impinges, substantially as described.

In witness whereof Ihave hereunto set my hand in presence of two witnesses.

ROBERT THOMSON.

Witnesses:

MATTHEW ATKINSON ADAM, GEORGE IsAAo BRIDGES. 

